Three Gorges Dam and the electric power systems in China Author:Author: ZZee Fu YuYujiejie WanWangg Supervisor: Erik Loxbo Examiner: Sven Johansson 2015-5-25 at BTH Acknowledgment Foremost, we would like to express our sincere gratitude to our professor and course manager Erik Loxbo. His patience and motivation were vital for the success of the project. His guidance helped us in the research and the writing of this thesis. Abstract In this thesis, we have mainly illustrated the hydropower engineering and power transmission technology in China. Through the comparison between the greatest hydro power station, the Three Gorges Dam, with some other great stations, we have obtained the hydro power technology is now quite mature and efficient in practice with 90% conversion rate. Afterwards, we have explained the procedures of how the kinetic energy and/or gravitational potential energy are transformed to electric power. And meanwhile, this thesis gave the detailed introductions with plenty diagrams to elaborate the working status of Three Gorges Dam and also the working theory of turbine. At last, this thesis showed the distributions of the constructed grids, and indicated the main high voltage AC and DC transmission lines which connect different grids in mainland of China. This huge project has covered over 1 billion people. Besides, we have given some suggestions for decreasing the damage from the earthquake and freezing to grids. And this thesis is ended with our analysis and conclusions for what we have studied above. Contents 1. Introduction ………………………………………………………… 1 2. History of the water power station ………………………………….. 2 First hydro electrical power in the world 3. Introduction of two important hydro electrical power stations ……… 2 Three Gorges Dam over Yangtze River Compare the largest and second largest hydro power station ‘Niagara’ hydropower station in USA 4. General Knowledge of Three Gorges Dam ………………………… 4 Advantages Disadvantages Environment influences Main Functions 5. The economical exploitation value and the developing level between China and the other countries over the world ………………………. 6 6. Generation Principles ………………………………………………… 9 Theory of hydro electrical power station The working theory of the generators Formula and parameters for turbines 7. Comparison of the capacity difference between a variety of generation methods The Statements of Present Grids …………… 14 Comparison of the capacity difference between a variety of generation methods Electricity power generating proportion The power grid construction Power transmission 8. Before Three Gorges Dam had been constructed, how did China grid regulate the grid frequency …………………………………… 15 9. Adjustment of Grids ………………………………………………… 16 How does the power station keep the same frequency with the grid How does the power station adjust when the frequency of the grid changes 10. Comparison the technique between HVDC technology and AC transmission …………………………………………………………. 18 Flexible AC Transmission Systems High voltage DC Advantage of HVDC Disadvantages of HVDC 11. The economy comparison between HVDC and AC transmission…19 HVDC has lower investment in overhead line Less investments in DC cable lines The investment for converter station is greater than the substation Less operating costs 12. Distribution of the grids in China ………………………………… 20 13. Earthquake and Freezing troubles for grids ……………………… 24 14. Blackouts and their impacts ……………………………………….. 25 15. Analysis ………………………………………………………………. 26 The status quo of Three Gorges Dam Efficiency and environment thinking of hydropower The significance of constructing national grid 16. Conclusions …………………………………………………………… 27 17. References .………………………………………………………….. 28 Introduction In this thesis, we have studied and analyzed the techniques of hydropower engineering and the power transmission system. It is the Three Gorges Dam that has the largest installed capacity(22.4GW) and annual generation capacity(98.8TWh). Through the comparison between the Three Gorges Dam and some other types of stations, we obtain that the hydropower technique is quite mature and works efficiently in practice now. Nowadays the hydropower conversion rate, which means the efficiency of the power transformation from kinetic and/or gravitational energy to electric power, has already reached up to 90%, while the thermal conversion rate is less than 60%, due to the heat sinking in power transformation. And the Three Gorges Dam was the most typical case in high efficiency power station. Afterwards, we have explained the theories about how the kinetic energy and/or gravitational potential energy are transformed to electric power. In hydropower system, the running water drives the turbines, and then, the generators on turbines start to work. Mechanical friction is the only cause of energy loss in the turbines. Hereafter, this thesis shows the distribution of the grids and some high voltage transmission projects, which are transmission lines plus substations, constructed in mainland of China. There are six separate grids in China, and these projects serve like bridges between grids and make them work as one. This huge electric net has covered over 1 billion people and has supplied 4190 TWh electric energy per year. This thesis gives detailed introductions with plenty diagrams to the working situation of Three Gorges Dam. For instance, we have compared the two largest hydroelectric power stations: Three Gorges Dam and Itaipu Dam. The Three Gorges Dam has 32 units while Itaipu has only 20. However, their annual generation capacities are almost the same. The reason is that the Three Gorges Dam not only generates electric power, but also controls the flow quantity. However, Itaipu just concentrates on power generation. What is more, the annual runoff of La Plata Parana River(where Itaipu located) is larger than Three Gorges of Yangtze River(where Three Gorges Dam located). Then the thesis illustrates how the generators in the dam work, and the theory for the power conversion as well. At last, we drew a map of Chinese grids distribution and another of the high voltage transmission lines deployed in China. China is the first country to run the ultra high voltage transmission system, and up till now, seven AC lines with one DC line which run over 1000kV have been deployed. They are effective in minimizing power losses in long distance transmission between different grids. We have investigated the distributions of high voltage AC lines and DC lines. The AC lines are mostly drawn between two cities, acting as the substation hubs, while the DC lines are usually drawn between electric power bases and the grids with high power demand. 128/ History of the water power station • First hydro electrical power in the world 1878France built the world's first hydropower station. After the 1930s, the development on quantities and capacities in hydropower were great. In the late 1980s, most industrialized countries, such as Switzerland and France had started to develop hydro power. In 20th century, the world's largest hydropower station, Itaipu, was built by Brazil and Paraguay jointly. It has 12.6 GW as its installed capacity. The world's first pumped storage power station was built in Switzerland in 1879 , which is called Lurton Pumped Storage Power Station. 1985, the pumped storage power station with the world’s largest installed capacity ,which is called Bath Visconti Pumped Storage Power Station, was put into operation in the United States The world's first tidal power station was built in 1913 by the coast of North Sea coast in Germany. The greatest tidal power station was in France , it is called ‘Rance’, with installed capacity 240 MW. In 1978, Japan built a wave power test boat called ‘Hamming’ , and it was the world's first large-scale wave energy power station. Introduction of two important hydro electrical power stations • Three Gorges Dam over Yangtze River [1] 1. The Three Gorges is the world’s largest hydropower station, and it was also the largest construction of the project in China in that period. 2. 1994 began to build, 2003 began to generate power and 2009 totally finished. 3. The dam is 185 meters on height, 2335 meters on length. 4. The water level is 175 meters on height. 5. The length of the reservoir is more than 600 Km. 6. The total investment is 95.46 billion CNY. 7. The total capacity is 22.4 GW, and there are 32 units, each unit has installed power 700 MW 228/ 8. Largest rate of flow 100,000 Cubic meters per second. 9. The Three Gorges Power Station generates up to 98.8 TWh per year. 10. Every year, this station equivalents to reduce burning more than 49 million tons of raw coal and nearly one hundred million tones of carbon dioxide emissions are eliminated. 11. If we calculate each kWh of electricity as 10 CNY (1CNY ≈ 1 SEK in 2014) for China’s GDP, the clean electricity generated by the Three Gorges Dam equivalents of contributing 1 trillion CNY on GDP. • Compare the largest and second largest hydro power station [2] The Three Gorges Itaipu Dam Size largest Second largest Place China Brazil Each Unit 700 MW 700 MW Number of Units 32 20 Total Capacity 22.4 GW 14 GW Largest annual 98.8 TWh 94.68 TWh generation capacity Height of dam 185 meters 176 meters Length of dam 2335 meters 7744 meters Height of the water 145-175 meters 1-3 meters (Table 1: The parameters comparison between the Three Gorges Dam and Itaipu Dam) The average power output of Three Gorges Dam has reached 84.7 TWh, but it was limited by the amount of water during the dry season. When wet season comes , it could use the endless rolling stream to generate more power. But because of the function of flood controlling, the water level would be reduced from 175 meters to 145 meters as table 1 shows, which resulted a lot of water has to be given up. So its average generation capacity was slightly less than the Itaipu power plant.